It is well known to provide underground drain lines at refineries and other industrial installations for disposing of surface water and possibly other liquids to remote locations where appropriate treatment and disposal takes place. It is also known to provide devices which allow for drainage of a liquid from a surface into a drain line or sewer while at the same time forming a liquid barrier to deter against the release or escape of gases from the sewer. An example of such a device is a drain apparatus with liquid trap which is the subject of co-pending, commonly assigned U.S. patent application Ser. No. 07/706,322, filed on May 28, 1991. Other devices are disclosed in U.S. Pat. No. 4,682,907, issued Jul. 28, 1987, U.S. Pat. No. 4,776,722, issued Oct. 11, 1988, U.S. Pat. No. 3,516,541, issued Jun. 23, 1970, and U.S. Pat. No. 3,556,993, issued Jan. 19, 1971.
The various forms of drain devices incorporating liquid traps are, of course, not absolute barriers to the emission of gases from the sewers or drain lines with which they are associated. That is, a gas pressure of sufficient magnitude in the line will cause displacement of water or other liquid in the traps and result in the venting of gases therethrough into the ambient atmosphere. This can result in the release of noxious and even dangerous vapors and gases.